Prednisone is among the most widely prescribed and at the same time also amongst the most controversial drugs in veterinary medicine. In high doses, it is utterly immune suppressive, offering it a status of a key drug in treating a wide range of inflammatory and immune-mediated disorders. The drug can even be life saving for dogs with Addison’s disease. Prednisone for dogs with cancer is often a major constituent of standard treatment protocols, especially for dogs with newly diagnosed cancer.
Reason for the Wide Use
The basic reason why prednisone is so widely used in lymphoma is it can bind to lymphoma cell membrane receptors and start faster tumor cell death. Moreover, it exerts a number of other advantages in dogs with cancer. Firstly it dramatically decreases fever and inflammation caused by the malignant cells, because of prednisone-induced up-regulation of manifestation of anti-inflammatory proteins and down-regulation of manifestation of pro-inflammatory proteins.
Prednisone administration also lowers concentration of blood calcium in animals with cancer-related hypercalcemia. This effect is mediated by reduced bone resorption of calcium, by blocking calcium resorption in the intestine, and by increasing calcium excretion through kidneys. All these effects combine to a rapid reduction of calcium in blood in dogs having hypercalcemia second to lymphoma.
Besides the therapeutic advantages, the low cost of the drug, its oral formulation and widespread availability are also reasons for its wide use by pet-owners as well as vets.
Cautions
Though prednisone seems to be like a panacea for dogs with cancer, you should be aware of certain factors. While about 50% of newly diagnosed cancer patients will have a dramatic lymph node size reduction and improvement in symptoms after starting the prednisone treatment, these positive effects are short-lived. Survival time of dogs with cancer and treated with prednisone often ranges from 1 to 3 months, as compared to the 10 to 15 months with other regular multidrug protocols.
While the drug initially may result in a partial reduction in lymphoma by destroying several of the malignant cells, those cells which are inherently resistant to the prednisone grow fast and mutate to turn more aggressive than the original lymphoma. This is also known as relapse or recurrence of lymphoma. And this relapsed lymphoma is usually resistant to future treatments with other chemotherapy drugs, causing short remission and survival time for the patient.
Prednisone treatment can also negatively influence the ability to make an accurate diagnosis of lymphoma. If there is dramatic reduction in lymph node size due to prednisone, there may not be enough number of lymphoma cells to diagnose correctly with standard tests like lymph node cytology, flow-cytometry, PCR or biopsy. The pet owner and the clinician then face a dilemma of deciding if to proceed with chemotherapy with not having a definitive diagnosis, or to stop prednisone and risk relapse of a chemotherapy-resistant lymphoma. If precise diagnosis is made, staging completed and tissue is collected for immnotyping, prednisone treatment for a few days is reasonable and is not risky, especially when the patient is not feeling well or if chemotherapy cannot be started immediately.